Second chambers and the informational function of parliamentary oversight: Written questions in Japan

This article examines how the institutional position of a second chamber is reflected in legislators’ use of written questions as oversight instruments. While studies of bicameralism have focused on legislative processes, veto power, and policy stability, less is known about how second chambers perform oversight through written questions. Using 16,369 written questions submitted to Japan’s House of Representatives and House of Councillors between 2001 and 2025, this article classifies each question into six functions and estimates logit models for each. The most robust finding is that House of Councillors-submitted written questions are more likely to be information-requesting, a relationship that remains after adding controls and excluding ambiguously classified observations; Firth-corrected estimates also produce similar coefficient magnitudes. Interpretation-confirming questions show a positive association only in some specifications. These findings suggest that second chambers can also serve as arenas for extracting government information and recording government views.